This invention relates to a filter system for a commercial deep fat fryer which permits recycling and filtering of the cooking oil with only a minimum of involvement by an operator. The filter system may also interconnect adjacent units whereby a single filter can be used sequentially to filter oil from multiple units.
Commercial deep fat frying units are used in restaurants to cook a wide variety of foods, including, for example, french fried potatoes, chicken and fish, and are used with batter coated foods in many instances.
Food items to be cooked are placed in a mesh basket and immersed in the hot cooking oil. As the oil circulates through the basket, cooked food particles become dislodged and drop out of the basket into the oil bath. It is necessary to filter the oil from time to time, and the rapidity with which such a filtering operation can be carried out is very important in a commercial fast food restaurant. It is preferred, then, to recycle the oil through a filter as quickly as possible.
In some prior art deep fat fryers, a sump is provided below heat tubes which extend through the oil bath. Food is cooked above the heat tubes and dislodged particles accumulate in the sump. The sump area below the heat tubes is at a lower temperature than the cooking bath and disagreeable flavors can develop from the over cooked food particles in the sump. Furthermore, if the sump is drained, filtered, and returned to the cooking bath it will be at a lower temperature than that required for cooking, necessitating reheating the oil before the cooking procedure can be repeated. In some instances, a separate heater is provided for the filtered oil before it is returned to the bath.
In U.S. Pat. No. 4,623,544 a weir is provided at the surface of the cooking bath and oil is continually allowed to flow over the weir and downward into a sump. The oil entering the sump is filtered, reheated, and continually re-injected into the oil bath. This can be heat inefficient because of the exposed piping to and from the heat exchanger.
In U.S. Pat. No. 3,977,973 a heat tube is provided in the lower portion of the bath and oil is withdrawn from the lower portion of the bath. The withdrawn oil flows through filters and is then re-injected into the bath adjacent the heat tubes. This device is capable of filtering on a continuous basis. The food particles, however, must first settle through the bath before they can be drained because oil is withdrawn from the lower portion of the bath only. This requires time, which can allow the food particles to transmit undesirable flavors into the cooking bath.
U.S. Pat. No. 5,404,799 describes a filter mechanism placed at the bottom of the tank containing the oil bath so that oil is continuously removed from the oil bath through the filter. Other related oil filtering systems are shown, for example, in U.S. Pat. No. 4,768,426 and is 4,962,698.
In co-pending patent application, Ser. No. 08/724,233, assigned to the assignee of this invention, there is described a continuous filtering system which includes a sump which is disposed beside the fryer tank so that oil from the surface of the tank will continuously spill over the edge of the tank into the sump whereupon it is recycled. This adds to the horizontal dimensions of the fryer in that the sump is disposed beside the fryer tank instead of below it. Dimensional requirements in fast food restaurants are very stringent. Typically, an oversized kitchen unit, whether it is a fryer or an oven, can not be used to replace a conventional unit, because there will not be sufficient space to accommodate the unit.
In co-pending application Ser. No. 09/390,284, a deep fat fryer is described wherein heat tubes extend through the tank and a filter system is provided below the tank. In such a filter system, it is desirable to remove the oil from the tank by gravity from the bottom of the tank and allow the oil to flow into a separate filter sump below the tank. The filtered oil is then pumped from the filter sump back into the tank. When it is desirable to change oil the separate filter sump can be removed and the used oil pumped therefrom into a waste container for disposal. There is a need, however, for an efficient means for achieving these functions in a filter system for one or more deep fat fryers which can be disposed below the fryer tank.
It has been discovered that a simplified and efficient filter system can be provided for commercial deep fat fryers wherein the system includes a filter sump, which is in the form of a pan slidably disposed below the fryer tank with wheels mounted thereon so that when it is desired to clean the tank or remove the used oil therefrom for disposal, the filter pan can be slidably displaced outwardly from the fryer unit for access. In addition, in a preferred embodiment of this invention a plurality of adjacent fryers could be serviced by a single filter pan with sequential filtering of the oil from each fryer unit.
In order to achieve sequential operation hand controls are provided in the front of each fryer and, typically, there are only two such controls. One control lever would open the tank valve so that the used oil can flow downwardly by gravity into the filter pan. The second control lever would activate or deactivate the return, by opening or closing a valve system, and tuning a pump on or off, simultaneously.
In operation, the oil will flow downwardly into a filter, pass through the filter, and then be pumped from the bottom of the pan through the filter so that the food particles will be left on top of the filter which is horizontally disposed in the filter pan. Cleaning is then simplified by lifting the filter out of the pan to dump the food particles into a waste container.
There are several improved features of the instant invention which dramatically increase the simplicity and efficiency of the filter system. There is a filter pickup tube which connects the filter and the pump to return filtered oil to the fryer. When it is necessary to clean the filter it is necessary to disconnect this tube. The tube however need not be removed from the fryer system because it is on a swivel attachment thereto. When it desired to clean the filter the end of the tube attached to the filter is freed and the entire tube is merely swiveled aside so that the filter can be lifted from its tank. In addition, the free end of the tube is attached to the filter by a seal engagement which remains intact even when there is debris residing in the filter pan and the filter is placed on top of it. The filter can be elevated while properly maintaining a seal. In this way, as debris builds in the filter pan the filter can rise up in a floating arrangement, as will be subsequently explained.
The filter itself includes a metal frame with upwardly extending handles so that the entire filter assembly, including the frame, can be removed quickly from the filter pan. Preferably the pickup tube is coupled to the metal frame by a rotatable coupling having a grip extension so that it can loosened quickly by hand.
The filter pan itself is slidably received in the fryer housing on opposed guide rails. Preferably the openings into the guide rails are tapered so that an operator can easily return the pan to its tracks after cleaning. The fryer of this invention further has a filter lid mounted on the fryer chassis or housing rather than on the filter pan and extending between the filter pan guide rails. Preferably the filter pan has integral sides which are contoured and casters are mounted on the lower surface at the distal end. The proximal end of the lower surface preferably has front skid feet, a handle, and a bull nose radius to allow the pan to roll over, for example, a rubber slip resistant safety mat normally located in the front of the fryer when the filter pan is removed. The combination of casters and the front handle on the filter pan allows the operator to move the pan on its rear casters in a fashion similar that used to move a suitcase on casters.
Furthermore, when the debris laden oil is transmitted from the fryer to the filter pan its passes through a downspout which is curved to allow the oil to spill across the filter pan at an acute angle rather than a perpendicular flow. The angled entry reduces the likelihood of splashing. The downspout is also swiveled and is movable between an open and a closed position. When the filter pan is pushed or pulled along its tracks it force the downspout to swivel between a substantially vertical position and a substantially horizontal position, with the latter being a closed position. This swiveled feature requires close tolerance in machine parts and O-rings to supply the necessary friction so that the spout will remain in place in its last position without free play.
Furthermore, a fixed axis universal joint is provided whereby precise alignment of the drain line can be provided regardless of dimensional variations introduced by adjacent or mating parts. The drain line itself may serve multiple fryers allowing a single filter pan for more than one fryers. In this instance the drain line should be of increasing diameter as it approaches the filter pan.
A unique three port valve is provided between the pump and the fryer tank so that when a single filter is used with multiple fryers the oil can be filtered sequentially and returned to the individual fryer by merely manipulating the valve on the return line. This feature permits reduction of the number of pipe joints and permits the adding of multiple fryers to a single pan. It will be necessary when operating the pump to provide for an anti-hammer effect in the return line by adding line compresses to reduce the overall system pressure.
Finally, the fryer of this invention is designed to provide the filter pan as optional rather than as a required unit so that if a customer desires to add a filter pan in the field this can be accomplished without providing a different cabinet. The cabinet or chassis maintains the same envelope with or without the filter pan.
Accordingly, it is an object of this invention to provide an efficient filtering system for one or more commercial deep fat fryers.
It is another object of this invention to provide a filter pan which is disposed below one or more fryers, and which may be slidably mounted in the lower portion of the fryer units and provided with wheels so that it can be easily moved from below the fryer units for access.
It is another object of this invention to provide a filter system in which a filter pan is disposed below the fryer tank with a horizontal filter therein consisting of paper, cloth, or other filter media supported on a horizontal frame so that oil from the tank drains down onto the filter, and passes through the filter, leaving cooked food particles on the outer surface of the filter.
It is a further object of this invention to provide a single filter pan for one or more adjacent units and a single pump with a three port valve so that when oil is drained from a single tank into the filter it can be returned to that same cooking tank whereby adjacent units can be sequentially filtered.
These and other objects will become readily apparent with reference to the drawings and the following description wherein: